Project Summary Title: Understanding the Importance of Place of Birth in Determining Old Age Cognitive Health and AD/ADRD Mortality Substantial geographic disparities in old age cognitive health and Alzheimer's Disease and Alzheimer's Dis- ease Related Dementia (AD/ADRD) mortality outcomes are well documented. Previous studies have linked old age cognitive health and AD risk to contemporaneous geographic, often neighborhood, contexts. However, by old age, over a third of the population has left their state of birth and an even greater share has left their county of birth, leaving the interpretation of contemporaneous links between geography and health clouded by endog- enous mobility and disregarding the importance of childhood exposures in producing the geographic disparities in health across the life course and into old age. Successfully unraveling the importance of life course expo- sures and decisions in producing geographic disparities in health at old ages has the potential to contribute to basic science as well as policy, but efforts have been hampered by a lack of large datasets with place of birth information. Our proposal takes advantage of newly available data on place of birth for over 5 million Ameri- cans born across the early to mid 20th century combined with our team's interdisciplinary background merging clinical research in AD, life course demography, economics, population health, and epidemiology of old age morbidity and mortality processes. Our overall aim is to uncover the extent to which place of birth has contributed to old age cognitive health and AD/ADRD mortality disparities by birth cohort, race/ethnic- ity, sex, and educational attainment in the US, and to explore the mechanisms underlying these rela- tionships. Our research team will leverage newly released and unique longitudinal data on millions of individu- als across multiple datasets containing rich measures of health processes in old age and mechanisms of early disease exposures, cumulative contextual disadvantage, and life course mobility. Using these data, we will pursue the following aims: (1) Aim 1: Create an ?Atlas of Birth of Place Impacts on AD/ADRD Mortality? (2) Determine the influence of birth place on disparities in old age cognitive health and AD/ADRD mortality by sex, race/ethnicity, and education and (3) Uncover mechanisms linking the relationship between place of birth and later health by focusing on mobility and early and cumulative exposures. Together, these aims will allow a par- adigm shift in how we understand old age health processes by integrating life course and spatial analysis into large scale analyses of the patterns and mechanisms of old age cognitive health and AD/ADRD mortality comes.